1. Field of the Invention
The present invention relates to a head cleaning device, an image forming apparatus, and a head cleaning method, and particularly to a cleaning technique of a liquid ejection surface of an ink jet head.
2. Description of the Related Art
As general-purpose image forming apparatuses, ink jet recording apparatuses that eject liquid from an ink jet head to form an image on a predetermined medium have been known. When an ink jet head is operated for a long period of time, solidified ink or paper dust of mediums and the like are attached to the ink ejection surface (nozzle surface) of the ink jet head. Particularly, when attached substances are attached to a nozzle opening for ink ejection or the vicinities thereof, abnormal ejection such as a deflection of the flight of ink or a reduction in the ejection amount occurs, and thus the image quality is deteriorated. In order to avoid such abnormal ink ejection, maintenance is periodically performed on the ink ejection surface of the ink jet head.
JP2001-130015A discloses a printing system for effectively removing foreign substances attached to a head surface of a printing head having a page width. Such a printing system is configured so that a cleaning cup is brought into contact with a printing head surface in which ink ejection orifices are opened, and the flow of cleaning liquid in the inside of the cleaning cup is switched from a first direction to a second direction opposite to the first direction, to thereby accelerate the cleaning liquid and generate shearing force in the flow of the cleaning liquid, and thus cleaning of the printing head surface is performed by causing the shearing force to act on the head surface.
As means for transporting a medium, a drum transport system that fixes a medium to the outer circumference surface of a cylindrically-shaped transport drum and rotates the transport drum to thereby move the medium in the circumferential direction of the transport drum is known. In such a drum transport system, a head is disposed so as to be inclined with respect to the horizontal plane so that the nozzle surface of the head and the medium (outer circumference surface of the transport drum) are parallel to each other. By adopting such an arrangement, cleaning liquid flows from the upper side of inclination to the lower side thereof when the cleaning liquid is supplied to the inclined nozzle surface, and thus it is difficult to uniformly supply the cleaning liquid to the entirety of the nozzle surface.
On the other hand, when a cleaning structure of a printing head according to JP2001-130015A is applied to the cleaning of the ink jet head disposed obliquely to the horizontal plane, corresponding to the drum transport system, there may be a case in which the cleaning liquid flows in the obliquely upward direction. When the flow of the cleaning liquid in the obliquely upward direction and the flow thereof in the obliquely downward direction occur, it is considered that a desired effect is not easily obtained.
The present invention is contrived in view of such circumstances, an object thereof is to provide a head cleaning device and an image forming apparatus and a head cleaning method which are capable of uniformly supplying cleaning liquid over the entirety of the nozzle surface of the head disposed so as to be obliquely inclined with respect to the horizontal plane.